There’s been another defection from the Gramercy Hotel’s Rose Bar — general manager Frank Roberts, who quit to start a new venture, The Brewster. He’s the latest to leave since Aby Rosen took over the Gramercy from Ian Schrager. The Brewster will be a restaurant and bar with an upstairs cafe on the corner of Mott and Broome streets, to open in September in time for Fashion Week. Meanwhile, Diego Garcia is hosting a Tuesday night party as part of Rosen’s plan to relaunch the Rose Bar.